Aluminium may be produced by electrolytic reactions in aluminium production electrolytic cells, sometimes called electrolytic smelting pots, using the Hall-Héroult process. An example of an electrolytic smelting pot is disclosed in US 2009/0159434.
The electrolytic reaction occurring in the electrolytic smelting pots produces effluent gas in the form of hot, particle-laden effluent gas, which is cleaned in a gas cleaning unit before being discharged to the atmosphere. An example of a gas cleaning unit for cleaning the effluent gas generated in electrolytic smelting pots is disclosed in U.S. Pat. No. 5,885,539. The gas cleaning unit disclosed in U.S. Pat. No. 5,885,539 comprises a first contact reactor and a second contact reactor. The effluent gas from the electrolytic smelting pots is first forwarded to the first contact reactor and is, in the first contact reactor, brought into contact with recycled alumina. The partly cleaned effluent gas is then forwarded to the second contact reactor and is, in the second contact reactor, brought into contact with fresh alumina. The partly used alumina is recycled from the second contact reactor to the first contact reactor. A dust removal device removes the alumina from the effluent gas which is then discharged to the atmosphere.